The word is spreading: Monarchs need milkweeds. They’re the
only plants their caterpillars will eat. It makes sense, then, that
people concerned with the drop in monarchs in the U.S. are
adding milkweeds to parks and backyard gardens. The plants’
stems and leaves provide an irreplaceable diet for caterpillars,
and the flowers feed adult butterflies and bees. But as many
gardeners will attest, those aren’t the only guests showing up
for dinner.
Expecting to find only hungry caterpillars, many gardeners are
alarmed when they see their milkweeds covered with tiny
orange bugs: oleander aphids. Just like monarch caterpillars,
these insects feed on the plants’ sap. They may be unsightly,
but they’re typically harmless.